Eye-testing device



March 13, 1928. 1,662,054

J. C. W. BEALL EYE TESTING DEVICE Filed July 30. 1926 Patented Mar. 13, 1928.

UNITED. STATES PATENT OFFICE.

EYE-TESTING DEVICE.

Application filed July 30,

The object of this invention is to produce a new and useful method of, and apparatus for, eye-testing, particularly for use in conjunction with the use of trial-frames.

In the drawing: I t Figure 1 is a front view of one form of apparatus with the cover removed. a i

Figure 2 is a section on the line A A of Figure 1, showing the cover in appropriate relation thereto. 7 r it is quite customary for persons to have 7 their eyes examined in the first instance by a specialist who uses appropriate drugs toparalyze the accommodative functlons of the eye during the examination, and who thereby can secure accurate measurements of the type and amount of the visual errors- However, it is likewise quite customary for. persons, after the typeot' theerrors has been deteru'iincd, to depend on occulists who use only trial-:t'rame tests without the use of: paralyzing drugs for the determination of variations in the required correction;

In this second type of examination errors will arise due to the exercise of the acc0mmodative action of the eyes. These errorsare generally of less magnitude than the dittercnces between lenses of the ophthalmic series, and when the same for both eyes will do little or no harm.

However, quite often the error will not be the same on both eyes, particularly when they require different corrections, and as a consequence the eyes will be under a con-. tinual strain due to the diiierence in accon1- modation required, and it is the purpose of this invention to eliminate, or at least mini mine, this difference of error The manner in which the error arises is as follows: One eye is tested, while the other is kept covered, and a suitable correction detern'iined by the trial-frame; and then this eye is QOYti'oLl, and a suitable correction "for the other is determined in a like manner. Either or both of these may be affected by the acconimodative power of the eye. Then the two eyes are tried together, or even sometimes by sliding the covers over them alter ately, and if no marked discrepancy appears the corrections are considerid sufficiently accurate. But in the test of he two eyes together a certain amount of mutual accommodation, i. e. accommodation of each to the deficiencies of the other, also comes into play and may render the respective corrections apparently consistent when they 1926. Serial- No. 126,039.

actually require different. accommodation by the two eyes. This difference, although not noticeable under these test conditions, soon.

manifests itself inthe usual symptoms of eye-strain. i

In order to avoid this difiiculty, after thecycle from one eye to the other and back to the first takes place in a period greater than that of persistence of vision and preferably less than the time required for a change in the accommodation oil the eyes. i

In this test, the eyes are provided with proper COIIGCUODS there will appear to be a single test object in a fixed position, while if the corrections are notproperly balanced the object will appear to behave accordingly. That is, if the lack of balanceis in spherical power the object will appear to flicker back and forth, or at certain speeds there may appear to be two objects at diflen ent distances,and if there is a dilference in prismatic correction the object will apparent ly jump up and down or sideways. The main thing in thistest is to change quickly from one eye to the other, as distinguished from the usual slow change by sliding a cover in the trial-frame and then removing the cover from the other eye. Due to the discontinuity of vision by each eye during this test there is much less opportunity for mutual accommodation to come into playthan in the: usual final test with both eyes simultaneously.

The form of the device preferred reason o t its simplicity and sturdiness is shown in the drawing, but many variations thereof will be obvious to one'skilled in the art, and,

in fact, almost any viewingshutter used in stereoscopic motion picture projection can be readily adapted to the purpose through slight changes. p

In the present form of the devicethe electrio motor (2),mounted on the base (1),- i

drives the shutter (5.) through the bevel friction-gear (9). The friction-gear is preferred because of its relative silence. The shutter is enclosed in the casing (4),

and is supported by the adjustable bearing 13 an the fixed bearing 14 it The sight holes (10) areprovided with glass covers (11) to prevent the entrance of dust. r

The upper end of the motor shaft (8), Which carries thefriction wheel (7), is supported by abearing (15) sliding in the block (16) and adjustable by means of the'screw (17) to provide the proper pressure on the from the foregoingdeseription,the patient wearing the trial-frame with substantially appropr ate lenses views the test chart through the holes (10) while the shutter is rotated at the approximate speed, and the trial lenses are then altered until freedom 7 The from jump of the image is secured. test may also be applied without the trialframes to determine if the eyes have similar characteristics.

m; i a e 1. 'lhevmethod =of test ng for balance 'between the eyescomprisingcausingthe patient to view a test object and then obscuring the vision of lns eyes'alternately, the period between successive obscurations of each eye being greater than, and the period between the obscurations of the two eyes being less than, the period ofpersistence of vision.

2. The methodbftesting for balance betweenthe eyes comprising causing the patient to view a test object through triallenses and then obscuring the vision of his eyes alternately, the period between successive obscurations of each eye being greater than,dand the period between the obscurations of the two eyes being less than, the

period. of persistence of vision.

3. The method of testing for balance be- "tween the eyes comprising causing the patient'to view a testobject through triallenses and then obscuring the vision of his eyes alternately, the period between successive obscurations of each eye being greater than, and the periodbetweentthe obscnrations of the two eyes being less than, the period of persistence, and altering the trial lensesuntih apparent immobility of the objectis secured. i

4. The method of testing for balance between vtheeyes comprising'causing the pa tient to view a test object through trial lenses and then obscuring the vision of his tions ofthe two eyes being less than, the period of persistence of vision, and altering the trial lenses until flicker of the image substantially disappears.

5.;Theinetl1od'of-testing for balance between the eyes comprising causing the patient to. view a test object through trial lenses and then obscuring thevision of his eyes alternately, the period between successive obscurations of each eye being greater than, and theperiod between the obscurations of the two eyes being less than, the period of persistence of vision, and altering the trial lenses until positional flicker of the image substantially disappears.

G. A device for use in eye-testing comprising means for obscuring the eyes alternately and a variable speed motor having ineans'for driving the obscuring means at a rate of from one but less than sixteen ohscurations per second. i i

7. A device for use in eye-testing comprising means for obscuring the eyes alternately and variable speed operating means fol-driving the obscuring means at a rate of not'less than one but less than sixteen obscurations per second.

8 Adevice for use in eye-testing comprising means tor'obscuring the eyes alternately and variable speed driving means for operating the obscuring means at such a rate that the periodbetween successive obscurations of eachv eye is greater than, and the period between obscurations of the alternate eyes is less than, the period of persistence of vision.

9. A devicefor use in eye-testing comprising a shutter adapted to obscure the eyes alternately, a; motor, and speed reduction drive meansconnccting the motor and shut ter and of such 'atio that the shutter will be driven at such-a speed that the-period between successive obscurations of eacheye will be greater than, and the period between obscurations of the alternate eyes will be less than, the period of persistence of vision.

10. Ardevice for use .in eye-testing comprising a shutter adaptedto obscure the eyes alternately, a motor, and speed reduction driving means connecting the motor and the shutter and of such ratio that the shutter will be driven thereby at a speed of not less than one but less than sixteen ohscurations per second. I

In testimony whereof I hereby afiix my signature.

JOHN o. W. BEALIL. 

